This invention relates to backpack assemblies of the type which are used by scuba divers to support a tank of breathing air. More particularly, the invention relates to a modular buoyancy compensator which includes a backpack assembly having its own harness system for attaching the backpack assembly to a diver and a separate inflatable air cell which can be releasably attached to the backpack for providing buoyancy compensation.
U.S. Pat. No. 5,046,894 describes a buoyancy compensator with interchangeable backpacks which can be removably attached to the buoyancy compensator. Buoyancy compensation is provided by a vest with an inflatable air cell inside the vest, and the vest includes shoulder straps for supporting a portion of the weight of the tank. The backpack cannot function as a stand-alone unit and has to be attached to the vest before the backpack can be used by a diver.
U.S. Pat. No. 4,990,115 describes a similar buoyancy compensator in which the harness system which supports the weight of the tank is an integral part of the inflatable air cell. In both the '894 and '115 patents the functions of tank support and buoyancy are not separated, and the air cell is required to support some of the load of the tank.
U.S. Pat. No. 4,752,263 describes a component system which contains an air cell, a backpack, and a weight drop system which assemble to each other. The backpack does not include a truss structure to distribute the load of the tank efficiently, and the backpack is constructed of a rigid, permanent material other than fabric. Further, the air cell does not define a specific control of buoyancy, either in the location of the buoyancy or the lift capacities. The backpack and air cell are custom designed and are not intended to be used with other backpacks or air cells.
U.S. Pat. No. 4,608,940 also describes a component system which includes an air cell, a backpack, and a weight drop system. The backpack is constructed of fabric and contains a waist closure and shoulder extensions which attach to the waist closure. However, the backpack does not provide the construction or function of a truss support system of harness and does not distribute the weight of the tank to the hips and shoulders of the diver.
U.S. Pat. No. 299,286 describes an "alpine pack system" which contains a rigid back subassembly which is attached to a neoprene shoulder harness subassembly to form a tank support system. The pack does not include shoulder extensions or a waist closure. The shoulders are provided by a fabric subassembly that stretches over and attaches to the rigid back form, and the pack uses a standard cummerbund configuration which does not contain a truss support system. The entire system must be assembled with an air cell in order to be functional.
U.S. Pat. No. 4,137,585 describes a buoyancy compensator which includes some of the features of the other patents.